#include<iostream>
using namespace std;

class Solution {
public:
    int mySqrt(int x)
    {
        long long left = 0, right = x;
        while (left < right)
        {
            long long mid = (right - left + 1) / 2 + left;
            if (mid * mid == x)
                return mid;
            else if (mid * mid < x)
                left = mid;
            else
                right = mid - 1;
        }
        return left;
    }
};